Cessna 150L accident near Bonners Ferry, Idaho, September 29, 1998
On September 29, 1998 at about 9:54 pm local time, a Cessna 150L, registered N19427, was substantially damaged in an accident near Bonners Ferry, Idaho. It was a personal flight under general aviation rules (Part 91). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
Improper maintenance by an outsourcing facility which resulted in a lack of identification of scoring of the interior of the #3 cylinder rocker shaft bosses. The scoring resulted in a fatigue fracture and subsequent permanent closure of both intake and exhaust valves. Contributing factors were the lack of a suitable landing site and trees.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- September 29, 1998 · about 9:54 pm local time
- Place
- Bonners Ferry, Idaho · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna 150L · all 150Ls on the register
- Registration
- N19427 · no longer on the register · serial 15074415
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
During the initial climb following a touch-and-go landing, the engine sputtered twice and the pilot-in-command initiated an emergency landing. The field of choice was obstructed with construction equipment and she chose an alternate field. She retarded the throttle to idle, lowered full flaps, and slipped the aircraft to land as expeditiously as possible; and then steered the aircraft into small trees and brush to avoid going over an embankment. Post-crash examination revealed all 3 bosses of the #3 cylinder broken, thus rendering the intake/exhaust valves permanently closed. Metallurgical examination revealed that the separation of the rocker arm shaft bosses was initiated by fatigue cracking in the boss located adjacent to the exhaust valve. Further examination revealed the presence of heavy tool marks on the bore surface of all three bosses. The heavy manual cutting of the bore surface is not authorized by the engine manufacturer and the surface created by this procedure did not meet the engine manufacturer requirements for surface finish in the bore of the bosses. A review of the aircraft's engine log revealed an overhaul 645.4 hours previous to the accident. The overhaul facility reported that all 4 cylinders were outsourced during the overhaul procedure.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: private
- Ratings: single-engine land
- Flight time: 266 hours in all; 239 in this make and model; 13 in the last 90 days; 3 in the last 30 days; 228 as pilot in command
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 5,306 hours
- Last inspection: annual inspection, March 4, 1998; 185 hours since
- Maximum gross weight: 1,600 lb
- Seats: 2
- Landing gear: fixed
- Engine: Continental O-200-A (piston); 0 hours total
The flight
- Departed from: 65S at 8:45 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 250° at 8 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 75°F (24°C), dew point 43°F (6°C)
- Altimeter: 30.00 inHg
- Observation at 9:54 pm from COE, 60 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.